Evaluating targeted and immunomodulatory therapies for melanoma in a genetically engineered mouse melanoma model

Melanoma therapy has changed rapidly due to the emergence of new therapies: MAPK-pathway targeted drugs and immunomodulatory agents. Given the relative success of these new individual drugs, this work set out to evaluate and develop effective melanoma treatments using combination therapies in a preclinical mouse melanoma models. Therapies tested include BRAF kinase inhibition in combination with: immune checkpoint inhibitors anti-CTLA4, anti-PDL1, and with the topical TLR7/8 agonist imiquimod. Drugs efficacies were tested in established melanomas in a conditional inducible mouse melanoma model based on activation of Braf and beta catenin and loss of Pten. BRAF inhibition in combination with anti-CTLA-4/anti-PD-L1 was not more effective than BRAF inhibition alone in retarding tumor growth or prolonging survival in these studies. Treatment with imiquimod significantly retarded tumor growth and increased survival. Imiquimod-treated tumors show increased macrophage infiltration, but not increased intratumoral T lymphocytes. Further work remains to identify effective, synergistic drug combinations in preclinical models.